1. Field of the Invention
The present invention relates to an image reading technique that generates a 2-dimensional code pattern including coded coordinates information, and reads recorded (or drawing) information with the 2-dimensional code pattern from a supporting medium on which the 2-dimensional code pattern is printed, and detects the locus of the recorded information.
More specifically, the present invention relates to a 2-dimensional code pattern that is printed with a document on a supporting medium without requiring special ink, and its generation technique that can reduce the reading error. The present invention relates to a 2-dimensional code reading technique that efficiently reads the printed 2-dimensional code pattern and processes the same on real time.
2. Description of the Related Art
The technique of specifying the position and the contents of the image information formed on a print medium, such as paper, by arranging the 2-dimensional code including the coded coordinates information on the print medium is known.
The conventional 1-dimensional bar code has information only horizontally. However, the 2-dimensional code has information to the horizontal direction and the vertical direction, and it can express more complicated information.
There is also known the technique that reads another image information with the 2-dimensional code pattern, inputs the read information into a data processing device, such as a computer, and processes the same in order to utilize the 2-dimensional code more effectively.
The 2-dimensional code symbol which can be read is optically arranged in the shape of a matrix on paper, and the technique which reads the 2-dimensional code symbol with the camera, and acquires coordinates information is known at the same time it corrects the paper with the pen equipped with the small camera. For example, Japanese Laid-Open Patent Application No. 2000-293303 discloses the above technique.
By this method, the information of the 2-dimensional code that is added by the handwriting on the paper can be read on real time, and the added information can be associated with the on-paper information before the handwriting, and the processed information can be stored.
There is also known the technique which uses the print medium of paper on which the pattern indicating the X coordinate and the Y coordinate, the pattern indicating the direction of the code, and the forming pattern, which is larger than the other patterns, are printed, and reproduces the recorded characters from the print medium. For example, U.S. Pat. No. 5,661,506 discloses the above technique.
The forming pattern and the other patterns are printed in the infrared ink on the print medium, and they are not visible with the human eyes. By reading these patterns optically, the coordinates positions of the characters written to the print medium with the usual marker are determined by the read information.
Furthermore, there is known the 2-dimensional code pattern which is constituted by the dots arranged and shifted by the predetermined amount in a different direction from the predetermined position, the 2-dimensional code pattern being able to represent two or more bits of information per dot. For example, the International Publication No. WO 00/73981 discloses the above 2-dimensional code pattern.
The 2-dimensional code pattern has the horizontal and vertical coordinates information, and when the 2-dimensional code is read, it is possible to acquire the positional information which is indicated by the 2-dimensional code on the paper.
In the above technique disclosed by Japanese Laid-Open Patent Application No. 2000-293303, the general-purpose 2-dimensional codes that are standardized by the AIM standard are arranged dispersedly, and the magnitude of each code is large. For this reason, in order to acquire the coordinates information indicated by the 2-dimensional codes, it is necessary to pickup the comparatively large region of the paper with the optical pen. As the image pickup region is wide, the quality of the read image will deteriorate due to the depth of field, and it will become difficult to correctly read the 2-dimensional codes continuously.
Moreover, the general-purpose 2-dimensional codes are not originally intended to acquire the coordinates information while it is visualized the paper during the writing with the camera, and it takes much time to complete the decoding of the read information, and it is difficult to process it on real time.
One of the major purposes of the above document is to acquire continuous drawing information, and if it cannot determine the coordinates positions continuously from the 2-dimensional codes, the discontinuity of the drawing information arises and it has the problem that the correct drawing information is not easily acquired.
In the above technique disclosed by U.S. Pat. No. 5,661,506, the infrared ink is used to print the 2-dimensional code pattern on the print medium with special printing equipment. The 2-dimensional code pattern cannot be embedded on the print medium by using a usual printer simultaneously with the time of printing the document on the print medium.
When the user prints the desired document and performs drawing correction on the paper where the infrared pattern is formed beforehand, correlation of the drawing information with the original electronic document cannot be produced, and only the drawing information will be reproduced.
In the technique disclosed by the International Publication No. WO 00/73981, by shifting the dots delicately from the 2-dimensional positions at regular intervals and arranging them, two or more bits of information are given to one dot, and the positional information of the code can be carried by the matrix of 6×6 dots.
However, in the above technique, the shifting amount is very small (30 micrometers). When the resolution (1200 dpi) of the widely-used laser printer is taken into account, it is difficult to reproduce the right amount of shifting because it requires the accuracy of paper feed, the rotating speed of the photoconductor etc.
Therefore, it is also necessary for the above technique to prepare the print medium on which the 2-dimensional code pattern is printed beforehand using a special printing technique, such as offset printing, and the problem that is essentially the same as that of U.S. Pat. No. 5,661,506 arises.